Core B: Cohort management and coordination of clinical research activities The overall aim of Core B is to support, the scientific investigations of the individual projects and the POl, while providing our study patients state-of-the-art clinical management of their Barrett's esophagus (BE) at three centers with expertise in the management of these patients to keep them safe from developing advanced incurable esophageal adenocarcinoma. Core B will continue longitudinal biospecimen collection in, and characterization of, an established cohort of patients who have Barrett's esophagus as well as to continue recruitment of new study patients at two additional study sites, to meet the aims of Projects 2 and 3 and the overall goals of the POl.The Seattle Barrett's Esophagus Research Study has a cohort of study patients who have Barrett's esophagus (BE), who represent various stages of progression to esophageal adenocarcinoma (EA), and from whom biopsies have been collected longitudinally and stored in our biorespository since 1989. Addition of two new study sites with standardized research protocols performed and monitored under the auspices of Core B, will allow the POl to retain its longitudinal cohort design while enrolling patients undergoing endoscopic therapy, not performed at our current study site, to meet the Aims of Projects 2 and 3. Specific Aim 1: To support the aims of the POl with the addition of two Core B study sites to ensure enrollment and longitudinal follow-up of new study patients with BE undergoing endoscopic therapy to meet the aims of Projects 2 and 3. Specific Aim 2: To support the overall POl by continuing longitudinal endoscopic biopsy acquisition over time in the same individual who is part of a wellcharacterized cohort of patients with BE for future validation studies, while maintaining our cohort study design. Specific Aim 3: To coordinate study patient recruitment, manage research-related activities and track patient safety, outcomes and protocol compliance at all three study sites to ensure full integration of the new study sites into Core B to meet the aims of the POl. RELEVANCE (See instructions): In Barrett's esophagus, the development of cancer is a dynamic process that evolves slowly over time in some patients, rapidly in others, or in most, remains stable without developing cancer. It is an ideal model to study the genomic evolution associated with the development of cancer over time because we are able to safely and periodically biopsy the same patient's Barrett's esophagus during long-term follow-up.